This invention relates to warp knit fabrics which contain highly activated carbon yarn and which are, accordingly, highly sorbent with respect to toxic chemical vapors.
Activated carbon yarns are generally produced by pyrolyzing in an inert atmosphere at an elevated temperature a yarn prepared from filaments of a polymeric carbonaceous material, such as viscose rayon, phenolic polymers, polyacrylonitrile, or other fiber-forming materials. After such yarns are pyrolyzed to convert the polymeric filaments into carbon filaments, the yarns are activated by controlled oxidation at even higher temperatures than those employed during the pyrolysis. This may be carried out in atmospheres of carbon dioxide or superheated steam or flue gas or air or even oxygen. The oxidation, when properly controlled with respect to a carbon yarn derived from a suitable precursor yarn subjected to a suitable pyrolysis reaction, results in a yarn made of fibers of noncrumbling carbon having a good distribution of pore sizes, thus providing a highly active yarn in terms of surface area available for sorption of toxic chemical vapors or gases and in terms of quantity of toxic chemical vapor or gas sorbed. Such highly activated carbon yarns and fabrics are described in an article entitled "Sorptive Textile Systems Containing Activated Carbon Fibers" by Gilbert N. Arons, Richard N. Macnair, Laurance G. Coffin, and Hubertina D. Hogan, Textile Research Journal, Vol. 44, No. 11, Nov. 1974,874-883, and in an article entitled "Activated Carbon Fabric Prepared by Pyrolysis and Activation of Phenolic Fabric" by Gilbert N. Arons and Richard N. Macnair, Textile Research Journal, Vol. 45, No. 1, January 1975, 91. Other relevant publications include the following articles: "Sorption Characteristics of Activated Carbon Fabric" by Gilbert N. Arons, Richard N. Macnair, and Richard L. Erickson, Textile Research Journal, Vol. 43, No. 9, September 1973, 539-543; and "Activated Carbon Fiber and Fabric Achieved by Pyrolysis and Activation of Phenolic Precursors" by Gilbert N. Arons and Richard N. Macnair, Textile Research Journal, Vol. 42, No. 1, January 1972, 60-63.
It is also known to produce woven protective clothing fabric made of activated carbon yarns in combinations with aromatic polyamide yarns which are flame-resistant, as disclosed in U.S. Pat. No. 3,744,534. Also, reinforced activated-carbon fabrics have been produced by laminating relatively weak activated carbon fabric to one or two non-carbon fabrics having good strength, thus providing support for the carbon fabric without substantially reducing the permeability of the fabric layers, including the activated carbon fabric layer, thus maintaining the ability of the activated carbon fabric to sorb toxic chemical vapors and gases while obtaining good strength and other desirable textile characteristics in the composite fabric, as disclosed in U.S. Pat. No. 3,850,785.
Weaving of fabrics containing activated carbon yarns has proven to be slow and expensive, and unadaptable to commercial weaving machinery and practices because of the very low strengths of activated carbon yarns. Hence, there has been no commercial development of activated carbon fabrics for protective clothing for use in areas where toxic chemical vapors create a serious hazard to life or health. It has been necessary, therefore, until now, for protective clothing to be made of materials of low permeability, such as polymeric foam overgarments impregnated with activated carbon because of the extremely high cost of woven fabrics made of or containing substantial quantities of active carbon yarns. Such materials create a severe problem in terms of comfort and greatly limit the time during which a human being can operate in an area containing toxic chemical vapors because of physiological stress due to excessive thermal insultion.
It is, therefore, an object of the invention to provide fabrics containing highly active carbon yarns which are suitable for use in making highly air-permeable clothing which will substantially completely sorb toxic chemcial vapor or gas agents present in air premeating such clothing, and which are capable of being produced on commercially available fabric-forming machines at or near current commercial production speeds.
Other objects and advantages will appear from the following description of the invention, and the novel features will be particularly pointed out in connection with the appended claims.